To spur Europe to meet ambitious CO₂ emission reduction targets, Greenpeace has developed scenarios for each country to increase its electricity generation from renewable sources. Energynautics was commissioned by Greenpeace to model and optimise the grid extensions in Europe necessary to integrate these large shares of renewables (77% of the total electricity supply by 2030, including 53% from wind and solar). The results and further analysis of the data are presented here. It was found that by preferring high voltage direct current rather than alternating current network extensions, the overall grid upgrades in Europe (measured as the length of new transmission lines) can be reduced by a third. By allowing a small amount of curtailment of variable renewable sources, a disproportionately large number of the necessary grid extensions can be avoided. In addition, the accuracy of decoupling active from reactive power flows is analysed.

This study addresses the development and operation of the European continental electricity system with a high penetration of wind and photovoltaic (PV) generation. The main focus of the work is the assessment of the impact of inertia reduction, due to wind and PV power electronics interface, on frequency stability indicators, as the rate of change of frequency and the frequency nadir following a large generation loss. The analysis is based on dynamic frequency stability studies, performed for every hour of the year and over a large number of weather scenarios. The outputs of these simulations are used to perform statistical analysis of these indicators and to estimate the critical instantaneous penetration rate of wind and PV, which the European continental synchronous area can accommodate from a system dynamics point of view. The results show that a single critical instantaneous penetration rate cannot be defined, since the frequency dynamic behaviour depends on parameters that change from one period to the following. Instead, this critical penetration rate should be calculated for every dispatch period. This study also highlights the growing importance of load self-regulating effect's contribution to frequency stability in the future system.

The need for inertial response provided by wind turbines (WTs) has been discussed in the industry for more than five years now. Yet, as of today only very few grid codes include specific requirements. Hence, the number of wind farms in commercial operation using such frequency control features is low, and knowledge of the real capabilities and limitations of inertial response from WTs is limited. The objective of this article was to summarise and to assess two years of operational experience with inertial response provided by type 4 WTs installed in a 138 MW wind farm in the Canadian province of Québec. In order to put the topic into context, existing and anticipated future grid code requirements in respect to inertial response as well as related performance criteria were summarised. Data from high-frequency measurement devices recorded at various operating conditions and grid situations was downloaded and processed. The actual performance was compared with the expected characteristics for each of the measurements, which allowed identifying areas for further development. Results of dynamic simulations demonstrated that the methodology and the models used for frequency control studies need to be improved.

Wind turbine generators (WTGs) equipped with the inertial response feature have been in operation on the Hydro-Québec system since 2012. As part of the validation and performance test program carried out at each wind power plant, on-line monitoring was used to evaluate the inertial response during under frequency events. This study presents the status of the ongoing assessment using field measurements and simulation results for type-III and type-IV WTGs equipped with the inertial response feature required by Hydro-Québec TransÉnergie since 2006.

In this study a flywheel (FW) system, which is integrated in the rotor of a wind turbine (WT), is proposed. It is made of hydraulic–pneumatic piston accumulators and its primary purpose is to provide the power system with inertia. Power system inertia is an essential premise for primary frequency control. The equations describing the system are presented. Simulation results show that the performance of such a FW system is superior to the commonly used approach of using WTs to provide the power system with so-called synthetic inertia.

The current study employs static and dynamic analysis configurations under different case studies in order to define the allocation, maximum capacity of non-conventional generation with emphasis on photovoltaic (PV), concentrating solar power (CSP) and wind energy technologies that may be inhabited within a region of a Mediterranean partner country. This work focuses on the impact that may induce any distributed units’ addition on the power system's load flow and transient stability. A group of substations were proposed to introduce the dispersed generation with the extension in mind to suggest the voltage level to connect these units. The main issues addressed were the total system losses and short-circuit capacity whereas among the most critical disturbances was a three-phase fault incident. Thermal and solar plants using basic machine models such as synchronous generator, exciter and governor and a wind farm employing doubly fed induction generator technology were chosen throughout this research study. The dynamic behaviour of the system elements was examined by changing the solar irradiance, applying a three-phase fault at the PV and wind power plant connected buses and by performing open-circuit setpoint step tests for one of the CSP exciter models. PSS®E software simulation tool of Siemens PTI will be utilised throughout this work.

This study proposes an algorithm for active and reactive power management in large photovoltaic (PV) power plants. The algorithm is designed in order to fulfil the requirements of the most demanding grid codes and combines the utilisation of the PV inverters, fixed switched capacitors and static synchronous compensators. The control algorithm is simulated as required by the grid codes and validated on a real 9.4 MW PV power plant.

An increasing number of energy storages will be installed in buildings with photovoltaic systems. However, batteries with only local operation tasks do not exhaust their technical potential. Using the available battery capacity in terms of power and energy to provide ancillary system services is therefore economically reasonable. Providing primary control reserve power in combination with increasing local self-sufficiency has been identified as a promising option for decentralised PV battery systems. Thereby, part of the battery capacity is used to provide grid services and the remaining part for the management and optimisation of local system operation. Provision of self-sufficiency increase is limited, when the battery's state of charge is within certain limits. In this study, it is shown that the simultaneous use of the battery to locally increase self-sufficiency reduces the need for external power sources to correct the storage level. The operational concept, the technical solutions, and a sensitivity analysis are presented. Furthermore, billing and measuring issues as well as the current regulatory framework conditions in Germany are discussed.

The reversible synchronous machines in a pumped station are put into operation frequently for effective operation of the hydro pumped-storage system. The detection of loss-of-excitation (LOE), which is a common failure for synchronous machines, must be guaranteed not only in normal operation, but also under starting and other possible operation conditions. A model of pumped-storage units under the starting condition was developed using the SimPowerSystems in Matlab/Simulink. The simulation results and real tests of a pumped-storage power plant in northeast China were presented. The LOE characteristics during starting were analysed for the first time. Since the frequency of voltage and current runs up gradually from zero to the rated frequency during starting, conventional LOE protections based on impedance under the rated frequency have to be disabled during starting. For this reason, a novel LOE protection was developed based on the R–L time-domain model and the least-square algorithm. Theoretical analysis and simulation tests demonstrate that the proposed LOE protection method is correct and valid.

This study examines the potential role of large-scale photovoltaics (PV) generation in addressing the economic, energy security and environmental challenges facing the electricity industry. A Monte-Carlo-based generation portfolio modelling tool is employed to examine the value and impacts of different PV penetrations in future electricity generation portfolios under future uncertainty and multiple industry objectives of minimising expected future costs, cost uncertainty and CO₂ emissions. The Australian National Electricity Market (NEM) facing highly uncertain future fossil-fuel prices, carbon price, plant capital costs and electricity demand was used as a case study. Hourly PV generations across diverse locations were simulated for different penetration levels. Modelling results show that, with relatively modest carbon prices, increased PV penetration leads to not only reductions in cost uncertainties and greenhouse gas emissions, but also the overall industry generation costs. This would greatly enhance the value and thus encourage investment in large-scale solar PV, even when the transmission cost estimates were included. The value of PV generation in future generation portfolios is also influenced by the mix of generation technologies. The findings from this study can assist in energy and climate policy decision making in the electricity industry, particularly with regard to large-scale PV generation and carbon pricing.

European energy policy guidelines recognise renewable energy sources the main mean to contrast the rapid fossil fuels depletion and the related global warming. Marine energy source represents an attractive and inexhaustible reservoir from which to draw. One of the major difficulties in integrating sea wave generation systems or equivalently wave energy converters (WECs) with existing electrical systems is the management of their generation intermittency. This is essentially due to the inherent nature of the sea wave source. Energy storage represents an effective enabling technology for mitigating such an effect. To this aim, this study proposes an efficient control strategy for embedded floating buoy generation systems with energy storage technologies in order to regularise the injected grid power while minimising the contractual power established by the distribution system operator. The control strategy has been tested numerically on a grid connected DC microgrid formed by a DC bus at which a floating buoy generation system is interfaced with an energy storage system, supercapacitors-based, having the purpose of smoothing the natural power fluctuations of the WEC.

Partial shading on photovoltaic (PV) array makes the task of operating the PV system at its peak power more complex due to multiple peak points on power–voltage (P–V) characteristic. Amongst multiple peaks, it is challenging to find global peak as there is a possibility of the system getting stuck at a local peak otherwise considerable loss of power may occur. In this study, experimental evaluation of a novel algorithm which tracks global peak is presented. The algorithm is capable of tracking the peak power under all partial shadowing and uniformly varying insolation conditions. The algorithm scans the entire P–V curve in larger steps by varying the duty cycle of DC–DC converter without missing any peak to determine approximate location of peak power point and then uses fuzzy logic to track the real global peak. The algorithm is verified through simulation and the results are validated through hardware implementation using TMS320F28335 digital signal processor. The experimental results match with the simulation results that justify the performance and robustness of the proposed algorithm for tracking global peak power when the PV array is partially shaded. The comparative evaluation of the proposed algorithm with conventional perturb and observe-based method is also carried out experimentally.

Photovoltaic (PV) arrays may be shaded by neighbouring buildings, power lines, trees, clouds, birds, grass and so on. This study begins by discussing the effects of partial shading on PV arrays characteristics and efficiency. It also provides a comparative literature review on methods used to mitigate these effects. Afterwards, this study proposes a novel unit called shading compensation unit (SCU). SCU is intended to alter the P–V characteristics of partially shaded arrays to become closer to these of non-shaded ones. Simulations are carried out using MATLAB/Simulink for different shading conditions and temperatures. The results show that SCUs enhance the maximum power of partially shaded arrays by 5–58%. Furthermore, maximum power of partially shaded arrays after adding SCUs is within 85–97% of an unshaded array (without SCUs) which significantly reduces intermittency of PV generation.

This study investigates the effects of series compensators, such as the dynamic voltage restorer (DVR), series dynamic braking resistor, thyristor switched series capacitor, and the high temperature superconducting fault current limiter (SFCL), in enhancing the transient stability of a doubly fed induction machine based variable speed wind generator system. The tested system consists of a 9 MW doubly fed induction generator based wind farm connected to an infinite bus through two step-up transformers and a double run transmission lines. A three-phase-to-ground (3LG) fault and a single-line-to-ground fault (1LG) were applied to one of the lines to demonstrate the transient stability enhancement ability of the series devices. A performance comparison among the four series compensators is made based on responses of active/reactive power, terminal voltage, rotor speed, dc link voltage, and current variations. Simulations were carried out in the MATLAB/Simulink environment. Simulation results show that all series devices can improve the transient stability, however, the SFCL is the most efficient in terms of active power, rotor speed stability and fault current suppression, and the DVR seems to have a better performance than the SFCL in terms of voltage and reactive power.